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Investigating the build-up of the Local Group galaxies with the CLUES simulation

Arendse, Nikki (2018) Investigating the build-up of the Local Group galaxies with the CLUES simulation. Master's Thesis / Essay, Astronomy.

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In this thesis the build-up of the Milky Way (MW), Andromeda (M31) and Triangulum (M33) is investigated using data from the CLUES simulation. The first part focuses on the evolution of metal-free (Population III) star over time, which are identified in the simulation as star particles with metallicities below a threshold of Z < 10^-4 Z_solar [Yoshida et al., 2004]. The fraction of metal-free stars is found to be decreasing strongly over time, such that at z = 0, there is no significant fraction of metal-free stars present in the current Local Group (LG) galaxies. The second part of the thesis examines the mass contribution of high-z Lyman Break Galaxies (LBGs) to the build-up of the MW, M31 and M33. Star particles from the CLUES simulation are linked to UV luminosities using the stellar population synthesis code Starburst99 [Leitherer et al., 1999]. For redshifts z ~ 5 - 10, the UV luminosity functions of CLUES progenitors are computed and compared to observational data points of LBGs, similar to the work of [Dayal et al., 2013]. With new data points, the LBGs overlap with the brightest CLUES progenitors in a magnitude interval of M_uv = -15 to -18. This demonstrates that the faintest LBGs currently known could have developed into structures similar to the MW. It is investigated how many of the CLUES progenitors from high redshift are still bound to the LG galaxies at z = 0, how much mass they contribute to the final structures and where they are located. A distinction is made between the bright progenitors (M_uv < -15, comparable to observed LBGs) and the faint progenitors (M_uv > -15). The most important conclusions that can be drawn from this analysis are the following: - Progenitor particles from lower redshifts contribute more mass to the galaxies at z = 0. - The fraction of gas particles that stays bound increases with decreasing redshift, which can be explained because at lower redshift minor mergers dominate over major mergers. Additionally, at lower redshifts galaxies have established larger gravitational potentials, therefore making it easier to hold onto their gas. - The bright progenitor’s star particles display a radial gradient, where the older star particles are embedded more in the centre of the galaxy. This trend is not observed in the faint progenitor’s stars, presumably because their longer merger time and smaller gravitational potential makes them more susceptible to tidal stripping.

Item Type: Thesis (Master's Thesis / Essay)
Supervisor name: Dayal, P.
Degree programme: Astronomy
Thesis type: Master's Thesis / Essay
Language: English
Date Deposited: 04 Nov 2018
Last Modified: 05 Nov 2018 11:20

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